1. Field of the Invention
The present invention relates to an electrical part with terminals, such as an encoder or a variable resistor, and to a structure for mounting the electrical part on a circuit board. More particularly, the present invention relates to a structure for mounting electrical parts of different types, which are similar in terminal arrangement, on the same circuit board.
2. Description of the Related Art
An electrical part with an operating member to be rotated, such as an encoder or a variable resistor, incorporates a slider and a conductive pattern on which the slider slides. The electrical part also has a plurality of terminals protruding outward therefrom. During mounting, the terminals are passed through terminal-insertion holes provided in a circuit board, and are soldered to an external circuit. The operating member is rotatable together with the slider or the conductive pattern. For example, in an encoder, a slider moves into contact with and away from a contact pattern with the rotation of an operating member, thereby outputting pulse signals. In a variable resistor, a slider slides on a resistor pattern with the rotation of an operating member, thereby changing the output resistance. In a case in which a push switch is provided under the operating member, the operating member can be not only rotated, but be pressed, and the push switch can be turned on by pressing down the operating member.
The type of such an electrical part, for example, an encoder can be changed only by using a contact pattern with a comb pattern having a different pitch. The type of a variable resistor can be changed only by using a resistor pattern having a different resistance characteristic. Therefore, multiple types of electrical parts can be produced at low cost without changing the basic configuration, and are widely used in various fields. For example, a common housing including a slider, terminals, and so on can be applied to a plurality of types of encoders which are different in the total number of pulses and in which a code plate having a contact pattern can rotate together with an operating member. In addition, since the housing can be insert-molded with a hoop material, the parts cost can be reduced substantially.
As described above, the electrical parts that are different in the total number of pulses can share the housing including a slider, terminals, and so on, and therefore, the cost can be reduced. However, problems arise because the electrical parts of different types are similar in appearance. That is, in a case in which electrical parts of different types that have similar terminal arrangements are mounted on the same circuit board, since terminal-insertion holes are similarly arranged in mounting regions corresponding to the electrical parts, terminals of an electrical part may be smoothly inserted in terminal-insertion holes provided in a wrong mounting region. This increases the danger of improperly mounting electrical parts. Furthermore, since mounting operation must be performed with the greatest care in order to prevent such improper mounting, working efficiency is reduced.